A word or phrase may be repeated for emphasis. That word or phrase may also be repeated in order to help us remember it. Both of these are true concerning the phrase in Psalm 99:3, namely, "for it is holy," referring to God's name; in verse 5 stating "for He is holy"; and in verse 9, where we read: "For the Lord our God is holy."
This last time the psalmist says this in connection with the truth that God answered the holy men of old, who called on Him, and forgave their sins. Now, that He is holy means that He is set apart, He is in a class by Himself. Not only is He cut off from all sin; but He and He only is God.
In what way does forgiving the sins of those that call upon Him make Him holy? In the sense that He is the only one Who can do that, and that He did it in the holy way of sending His own Son to suffer our punishment and be raised as Our Head, and through Him conquered death and the grave. In our salvation, as well as being the sovereign God Who rules all things, and in righteous judgment establishes equity, He is in a class by Himself, the highly exalted and only God.
Our versification sings it thus:
Holy men of old in Him alone confided;
He forgave their sins,
Although they felt His chastening rod;
In His holy temple worship and adore Him,
Faithful and holy is the Lord our God.
You may notice that in verse 9 we are called to worship Him "at His holy hill." That means at His temple. And that temple was built on a hill in Jerusalem. This was not incidental or accidental but by the design of God. He is high above all creation. His typical dwelling place must also be a place to which we ascend. And when we are told to exalt Him, the idea is that in our minds we are to see Him as the sovereign God Who is high above all things and worthy of the highest praise and worship. Look up then to Him and worship Him as God alone and our only hope of salvation.
Song for Meditation: (Scottish Psalter) Psalm 23
Why not sing along??
"Worship should be somewhat like its object --Great praise for a great God. There is no part of Jehovah's greatness which is not worthy of great praise. In some beings, greatness is but vastness of evil: in Him it is magnificence of goodness. Praise may be said to be great when the song contains great matter, when the hearts producing it are intensely fervent, and when large numbers unite in the grand acclaim. No chorus is too loud, no orchestra too large, no psalm too lofty for the lauding of the Lord of Hosts." C. H. Spurgeon on Psalm 145:3